The relationship between chironomids and climate in high latitude Eurasian lakes: implications for reconstructing Late Quaternary climate variability from subfossil chironomid assemblages in lake sediments from northern Russia

This thesis investigates climate variability during the Late Quaternary in northern Russia by analysis of subfossil Chironomid assemblages in lake sediment cores. The modern chironomid fauna was determined in surface-sediment samples from 94 lakes, located between 61° - 72°N and 52° - 131°E. The influence of chemical and physical environmental variables on the distribution and abundance of taxa was investigated using multivariate analysis and modelling of taxon responses. Chironomid distribution showed a statistically strong relationship to mean July air temperature and continentality, and inference models were developed to reconstruct these variables. Palaeoclimate reconstructions for the past 700 years are presented from lakes on the Putoran Plateau, western Siberia (68°N, 92°E). These reconstructions show that whilst July air temperatures have remained relatively stable over the last 50 years, continentality has declined, resulting in a longer growing season. The results also enabled the models to be validated against instrumental records. Reconstructions are then presented from lakes in north-east European Russia: Lake Kharinei, (67.36°N, 62.75°E) where sedimentation started approximately 12600 cal. yrs BP, and a mid-Holocene sequence (4500 – 6500 cal. yr BP) from VORK5 (67.86°N, 59.03°E). The chironomid-inferred reconstructions suggest the early Holocene was approximately 2°C warmer than present with a more continental climate. July air temperatures then declined but remained warmer than present until 6000 yrs BP. From approximately 6000 yrs BP, July temperatures declined and the climate became more continental, indicating a shift to short cool summers. Combined use of the July air temperature and continentality inference models enhances the explanatory power of the palaeoenvironmental reconstructions and helps to reconcile apparent discrepancies with other proxy records. The results improve our understanding of the nature and timing of climate change, such as the spatial extent of the Younger Dryas, in poorly-studied regions of northern Eurasia

Temperature change as a driver of spatial patterns and long-term trends in chironomid (Insecta: Diptera) diversity

Anthropogenic activities have led to a global decline in biodiversity, and monitoring studies indicate that both insect communities and wetland ecosystems are particularly affected. However, there is a need for long-term data (over centennial- or millennial timescales) to better understand natural community dynamics and the processes that govern the observed trends. Chironomids (Insecta: Diptera: Chironomidae) are often the most abundant insects in lake ecosystems, sensitive to environmental change, and, because their larval exoskeleton head capsules preserve well in lake sediments, they provide a unique record of insect community dynamics through time. Here, we provide the results of a meta-data analysis of chironomid diversity across a range of spatial and temporal scales. First, we analyse spatial trends in chironomid diversity using Northern Hemispheric datasets overall consisting of 837 lakes. Our results indicate that in most of our datasets summer temperature (Tjul) is strongly associated with spatial trends in modern-day chironomid diversity. We observe a strong increase in chironomid alpha diversity with increasing Tjul in regions with present day Tjul between 2.5-14 °C. In some areas with Tjul >14 °C chironomid diversity stabilises or declines. Second, we demonstrate that the direction and amplitude of change in alpha diversity in a compilation of subfossil chironomid records spanning the last glacial-interglacial transition (~15,000-11,000 years ago) are similar to those observed in our modern data. A compilation of Holocene records shows that during phases when the amplitude of temperature change was small, site-specific factors had a greater influence on the chironomid fauna obscuring the chironomid diversity-temperature relationship. Our results imply expected overall chironomid diversity increases in colder regions such as the Arctic under sustained global warming, but with complex and not necessarily predictable responses for individual sites

The distribution and abundance of chironomids in high-latitude Eurasian lakes with respect to temperature and continentality: development and application of new chironomid-based climate-inference models in northern Russia

The large landmass of northern Russia has the potential to influence global climate through amplification of climate change. Reconstructing the climate in this region over millennial timescales is crucial for understanding the processes that affect the climate system. Chironomids, preserved in lake sediments, have the potential to produce high resolution, low error, quantitative summer air temperature reconstructions. Canonical correspondence analysis (CCA) of modern surface sediments from 100 high-latitude lakes, located in northern European Russia to central Siberia, showed chironomid distribution was primarily driven by July air temperatures. The strong relationship enabled the development of chironomid-inference model based on 81 lake and 89 taxa to reconstruct July air temperature. Analysis of a range of chironomid-inferred temperature model suggest the best to be a two component weighted averaging and partial least squares (WA-PLS model) with r2jack = 0.92 and RMSEP = 0.89°C. Comparison of species responses to July temperature with the Norwegian training set showed the temperature optima of individual species was 1-3°C in the Russian data regardless of modelling technique. This suggests that chironomid-based inference models should only be applied to sediment cores collected within the geographic source area of the training set. The differing responses between the Norwegian and Russian faunas led to the development of a 149 lake, 120 taxa chironomid-continentality inference model. The 2-component WA-PLS model was the minimal adequate model with r2jack = 0.73 and RMSEP = 9.9. Recent warming in the Arctic has been spatial and seasonal heterogeneous; in many areas warming is more pronounced in the spring and autumn leading to a lengthening of the summer, while summer temperatures have remained relatively stable. A continentality model has the potential to detect these seasonal changes in climate. The Russian inference model also improves the representation of a number of taxa, such as Corynocera oliveri-type, Constempellina and Paracladius, which frequently occur in subfossil assemblages from arctic Russian lakes, but are poorly represented in European training sets. These are cold-adapted taxa and their absence from the training sets could lead to overestimations of July temperatures in fossil samples where these taxa form a major component (for example see Andreev et al. 2005). Comparison of reconstructed July air temperatures and continentality indices from a tundra lake in north-east European Russia showed close agreement with local instrumental records over the past 70 years and suggests the models may produce reliable estimates of past climate

Cost-effectiveness of Internet Interventions Compared With Treatment as Usual for People With Mental Disorders:Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND: The economic costs of mental disorders for society are huge. Internet-based interventions are often coined as cost-effective alternatives to usual care, but the evidence is mixed. OBJECTIVE: The aim was to review the literature on the cost-effectiveness of internet interventions for mental disorders compared with usual care and to provide an estimate of the monetary benefits of such interventions compared with usual care. METHODS: A systematic review and meta-analysis of randomized controlled trials was conducted, which included participants with symptoms of mental disorders; investigated a telephone- or internet-based intervention; included a control condition in the form of treatment as usual, psychological placebo, waiting list control, or bibliotherapy; reported outcomes on both quality of life and costs; and included articles published in English. Electronic databases such as PubMed (including MEDLINE), Embase, Emcare, PsycINFO, Web of Science, and the Cochrane Library were used. Data on risk of bias, quality of the economic evaluation, quality-adjusted life years, and costs were extracted from the included studies, and the incremental net benefit was calculated and pooled. RESULTS: The search yielded 6226 abstracts, and 37 studies with 14,946 participants were included. The quality of economic evaluations of the included studies was rated as moderate, and the risk of bias was high. A random-effects approach was maintained. Analyses suggested internet interventions were slightly more effective than usual care in terms of quality-adjusted life years gain (Hedges g=0.052, 95% CI 0.010-0.094; P=.02) and equally expensive (Hedges g=0.002, 95% CI −0.080 to 0.84; P=.96). The pooled incremental net benefit was US $255 (95$91 to US $419; P=.002), favoring internet interventions over usual care. The perspective of the economic evaluation and targeted mental disorder moderated the results. CONCLUSIONS: The findings indicate that the cost-effectiveness of internet interventions for mental disorders compared with a care-as-usual approach is likely, but generalizability to new studies is poor given the substantial heterogeneity. This is the first study in the field of mental health to pool cost-effectiveness outcomes in an aggregate data meta-analysis. TRIAL REGISTRATION: PROSPERO CRD42019141659; https://tinyurl.com/3cu99b3